drivers/rtc/sysfs.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * RTC subsystem, sysfs interface
   4  *
   5  * Copyright (C) 2005 Tower Technologies
   6  * Author: Alessandro Zummo <a.zummo@towertech.it>
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/rtc.h>
  11
  12 #include "rtc-core.h"
  13
  14 /* device attributes */
  15
  16 /*
  17  * NOTE:  RTC times displayed in sysfs use the RTC's timezone.  That's
  18  * ideally UTC.  However, PCs that also boot to MS-Windows normally use
  19  * the local time and change to match daylight savings time.  That affects
  20  * attributes including date, time, since_epoch, and wakealarm.
  21  */
  22
  23 static ssize_t
  24 name_show(struct device *dev, struct device_attribute *attr, char *buf)
  25 {
  26         return sprintf(buf, "%s %s\n", dev_driver_string(dev->parent),
  27                        dev_name(dev->parent));
  28 }
  29 static DEVICE_ATTR_RO(name);
  30
  31 static ssize_t
  32 date_show(struct device *dev, struct device_attribute *attr, char *buf)
  33 {
  34         ssize_t retval;
  35         struct rtc_time tm;
  36
  37         retval = rtc_read_time(to_rtc_device(dev), &tm);
  38         if (retval)
  39                 return retval;
  40
  41         return sprintf(buf, "%ptRd\n", &tm);
  42 }
  43 static DEVICE_ATTR_RO(date);
  44
  45 static ssize_t
  46 time_show(struct device *dev, struct device_attribute *attr, char *buf)
  47 {
  48         ssize_t retval;
  49         struct rtc_time tm;
  50
  51         retval = rtc_read_time(to_rtc_device(dev), &tm);
  52         if (retval)
  53                 return retval;
  54
  55         return sprintf(buf, "%ptRt\n", &tm);
  56 }
  57 static DEVICE_ATTR_RO(time);
  58
  59 static ssize_t
  60 since_epoch_show(struct device *dev, struct device_attribute *attr, char *buf)
  61 {
  62         ssize_t retval;
  63         struct rtc_time tm;
  64
  65         retval = rtc_read_time(to_rtc_device(dev), &tm);
  66         if (retval == 0) {
  67                 time64_t time;
  68
  69                 time = rtc_tm_to_time64(&tm);
  70                 retval = sprintf(buf, "%lld\n", time);
  71         }
  72
  73         return retval;
  74 }
  75 static DEVICE_ATTR_RO(since_epoch);
  76
  77 static ssize_t
  78 max_user_freq_show(struct device *dev, struct device_attribute *attr, char *buf)
  79 {
  80         return sprintf(buf, "%d\n", to_rtc_device(dev)->max_user_freq);
  81 }
  82
  83 static ssize_t
  84 max_user_freq_store(struct device *dev, struct device_attribute *attr,
  85                     const char *buf, size_t n)
  86 {
  87         struct rtc_device *rtc = to_rtc_device(dev);
  88         unsigned long val;
  89         int err;
  90
  91         err = kstrtoul(buf, 0, &val);
  92         if (err)
  93                 return err;
  94
  95         if (val >= 4096 || val == 0)
  96                 return -EINVAL;
  97
  98         rtc->max_user_freq = (int)val;
  99
 100         return n;
 101 }
 102 static DEVICE_ATTR_RW(max_user_freq);
 103
 104 /**
 105  * rtc_sysfs_show_hctosys - indicate if the given RTC set the system time
 106  *
 107  * Returns 1 if the system clock was set by this RTC at the last
 108  * boot or resume event.
 109  */
 110 static ssize_t
 111 hctosys_show(struct device *dev, struct device_attribute *attr, char *buf)
 112 {
 113 #ifdef CONFIG_RTC_HCTOSYS_DEVICE
 114         if (rtc_hctosys_ret == 0 &&
 115             strcmp(dev_name(&to_rtc_device(dev)->dev),
 116                    CONFIG_RTC_HCTOSYS_DEVICE) == 0)
 117                 return sprintf(buf, "1\n");
 118 #endif
 119         return sprintf(buf, "0\n");
 120 }
 121 static DEVICE_ATTR_RO(hctosys);
 122
 123 static ssize_t
 124 wakealarm_show(struct device *dev, struct device_attribute *attr, char *buf)
 125 {
 126         ssize_t retval;
 127         time64_t alarm;
 128         struct rtc_wkalrm alm;
 129
 130         /* Don't show disabled alarms.  For uniformity, RTC alarms are
 131          * conceptually one-shot, even though some common RTCs (on PCs)
 132          * don't actually work that way.
 133          *
 134          * NOTE: RTC implementations where the alarm doesn't match an
 135          * exact YYYY-MM-DD HH:MM[:SS] date *must* disable their RTC
 136          * alarms after they trigger, to ensure one-shot semantics.
 137          */
 138         retval = rtc_read_alarm(to_rtc_device(dev), &alm);
 139         if (retval == 0 && alm.enabled) {
 140                 alarm = rtc_tm_to_time64(&alm.time);
 141                 retval = sprintf(buf, "%lld\n", alarm);
 142         }
 143
 144         return retval;
 145 }
 146
 147 static ssize_t
 148 wakealarm_store(struct device *dev, struct device_attribute *attr,
 149                 const char *buf, size_t n)
 150 {
 151         ssize_t retval;
 152         time64_t now, alarm;
 153         time64_t push = 0;
 154         struct rtc_wkalrm alm;
 155         struct rtc_device *rtc = to_rtc_device(dev);
 156         const char *buf_ptr;
 157         int adjust = 0;
 158
 159         /* Only request alarms that trigger in the future.  Disable them
 160          * by writing another time, e.g. 0 meaning Jan 1 1970 UTC.
 161          */
 162         retval = rtc_read_time(rtc, &alm.time);
 163         if (retval < 0)
 164                 return retval;
 165         now = rtc_tm_to_time64(&alm.time);
 166
 167         buf_ptr = buf;
 168         if (*buf_ptr == '+') {
 169                 buf_ptr++;
 170                 if (*buf_ptr == '=') {
 171                         buf_ptr++;
 172                         push = 1;
 173                 } else {
 174                         adjust = 1;
 175                 }
 176         }
 177         retval = kstrtos64(buf_ptr, 0, &alarm);
 178         if (retval)
 179                 return retval;
 180         if (adjust)
 181                 alarm += now;
 182         if (alarm > now || push) {
 183                 /* Avoid accidentally clobbering active alarms; we can't
 184                  * entirely prevent that here, without even the minimal
 185                  * locking from the /dev/rtcN api.
 186                  */
 187                 retval = rtc_read_alarm(rtc, &alm);
 188                 if (retval < 0)
 189                         return retval;
 190                 if (alm.enabled) {
 191                         if (push) {
 192                                 push = rtc_tm_to_time64(&alm.time);
 193                                 alarm += push;
 194                         } else
 195                                 return -EBUSY;
 196                 } else if (push)
 197                         return -EINVAL;
 198                 alm.enabled = 1;
 199         } else {
 200                 alm.enabled = 0;
 201
 202                 /* Provide a valid future alarm time.  Linux isn't EFI,
 203                  * this time won't be ignored when disabling the alarm.
 204                  */
 205                 alarm = now + 300;
 206         }
 207         rtc_time64_to_tm(alarm, &alm.time);
 208
 209         retval = rtc_set_alarm(rtc, &alm);
 210         return (retval < 0) ? retval : n;
 211 }
 212 static DEVICE_ATTR_RW(wakealarm);
 213
 214 static ssize_t
 215 offset_show(struct device *dev, struct device_attribute *attr, char *buf)
 216 {
 217         ssize_t retval;
 218         long offset;
 219
 220         retval = rtc_read_offset(to_rtc_device(dev), &offset);
 221         if (retval == 0)
 222                 retval = sprintf(buf, "%ld\n", offset);
 223
 224         return retval;
 225 }
 226
 227 static ssize_t
 228 offset_store(struct device *dev, struct device_attribute *attr,
 229              const char *buf, size_t n)
 230 {
 231         ssize_t retval;
 232         long offset;
 233
 234         retval = kstrtol(buf, 10, &offset);
 235         if (retval == 0)
 236                 retval = rtc_set_offset(to_rtc_device(dev), offset);
 237
 238         return (retval < 0) ? retval : n;
 239 }
 240 static DEVICE_ATTR_RW(offset);
 241
 242 static ssize_t
 243 range_show(struct device *dev, struct device_attribute *attr, char *buf)
 244 {
 245         return sprintf(buf, "[%lld,%llu]\n", to_rtc_device(dev)->range_min,
 246                        to_rtc_device(dev)->range_max);
 247 }
 248 static DEVICE_ATTR_RO(range);
 249
 250 static struct attribute *rtc_attrs[] = {
 251         &dev_attr_name.attr,
 252         &dev_attr_date.attr,
 253         &dev_attr_time.attr,
 254         &dev_attr_since_epoch.attr,
 255         &dev_attr_max_user_freq.attr,
 256         &dev_attr_hctosys.attr,
 257         &dev_attr_wakealarm.attr,
 258         &dev_attr_offset.attr,
 259         &dev_attr_range.attr,
 260         NULL,
 261 };
 262
 263 /* The reason to trigger an alarm with no process watching it (via sysfs)
 264  * is its side effect:  waking from a system state like suspend-to-RAM or
 265  * suspend-to-disk.  So: no attribute unless that side effect is possible.
 266  * (Userspace may disable that mechanism later.)
 267  */
 268 static bool rtc_does_wakealarm(struct rtc_device *rtc)
 269 {
 270         if (!device_can_wakeup(rtc->dev.parent))
 271                 return false;
 272
 273         return rtc->ops->set_alarm != NULL;
 274 }
 275
 276 static umode_t rtc_attr_is_visible(struct kobject *kobj,
 277                                    struct attribute *attr, int n)
 278 {
 279         struct device *dev = container_of(kobj, struct device, kobj);
 280         struct rtc_device *rtc = to_rtc_device(dev);
 281         umode_t mode = attr->mode;
 282
 283         if (attr == &dev_attr_wakealarm.attr) {
 284                 if (!rtc_does_wakealarm(rtc))
 285                         mode = 0;
 286         } else if (attr == &dev_attr_offset.attr) {
 287                 if (!rtc->ops->set_offset)
 288                         mode = 0;
 289         } else if (attr == &dev_attr_range.attr) {
 290                 if (!(rtc->range_max - rtc->range_min))
 291                         mode = 0;
 292         }
 293
 294         return mode;
 295 }
 296
 297 static struct attribute_group rtc_attr_group = {
 298         .is_visible     = rtc_attr_is_visible,
 299         .attrs          = rtc_attrs,
 300 };
 301
 302 static const struct attribute_group *rtc_attr_groups[] = {
 303         &rtc_attr_group,
 304         NULL
 305 };
 306
 307 const struct attribute_group **rtc_get_dev_attribute_groups(void)
 308 {
 309         return rtc_attr_groups;
 310 }
 311
 312 int rtc_add_groups(struct rtc_device *rtc, const struct attribute_group **grps)
 313 {
 314         size_t old_cnt = 0, add_cnt = 0, new_cnt;
 315         const struct attribute_group **groups, **old;
 316
 317         if (rtc->registered)
 318                 return -EINVAL;
 319         if (!grps)
 320                 return -EINVAL;
 321
 322         groups = rtc->dev.groups;
 323         if (groups)
 324                 for (; *groups; groups++)
 325                         old_cnt++;
 326
 327         for (groups = grps; *groups; groups++)
 328                 add_cnt++;
 329
 330         new_cnt = old_cnt + add_cnt + 1;
 331         groups = devm_kcalloc(&rtc->dev, new_cnt, sizeof(*groups), GFP_KERNEL);
 332         if (!groups)
 333                 return -ENOMEM;
 334         memcpy(groups, rtc->dev.groups, old_cnt * sizeof(*groups));
 335         memcpy(groups + old_cnt, grps, add_cnt * sizeof(*groups));
 336         groups[old_cnt + add_cnt] = NULL;
 337
 338         old = rtc->dev.groups;
 339         rtc->dev.groups = groups;
 340         if (old && old != rtc_attr_groups)
 341                 devm_kfree(&rtc->dev, old);
 342
 343         return 0;
 344 }
 345 EXPORT_SYMBOL(rtc_add_groups);
 346
 347 int rtc_add_group(struct rtc_device *rtc, const struct attribute_group *grp)
 348 {
 349         const struct attribute_group *groups[] = { grp, NULL };
 350
 351         return rtc_add_groups(rtc, groups);
 352 }
 353 EXPORT_SYMBOL(rtc_add_group);